/* ─── Variables ─────────────────────────────────────────────── */
:root {
  --bg: #FFFFFF;
  --bg-alt: #F9FAFB;
  --text: #1F2937;
  --text-secondary: #6B7280;
  --accent: #2563EB;
  --accent-secondary: #06B6D4;
  --accent-light: rgba(37, 99, 235, 0.07);
  --border: #E5E7EB;
  --card: #FFFFFF;
  --shadow: 0 1px 3px rgba(0,0,0,0.07), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
  --radius: 10px;
}

[data-theme="dark"] {
  --bg: #0F172A;
  --bg-alt: #1E293B;
  --text: #F1F5F9;
  --text-secondary: #94A3B8;
  --accent: #3B82F6;
  --accent-secondary: #22D3EE;
  --accent-light: rgba(59, 130, 246, 0.1);
  --border: #334155;
  --card: #1E293B;
  --shadow: 0 1px 3px rgba(0,0,0,0.4);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
}

/* ─── Reset ─────────────────────────────────────────────────── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; overflow-x: hidden; }

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

* { transition: background-color 0.25s ease, color 0.25s ease, border-color 0.25s ease; }

a { color: inherit; text-decoration: none; }

/* ─── Navigation ─────────────────────────────────────────────── */
.nav {
  position: fixed;
  top: 0; left: 0;
  width: 100%;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  z-index: 1000;
  transition: transform 0.3s ease, background-color 0.25s ease;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.nav.hidden { transform: translateY(-100%); }

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
}

.nav-logo {
  display: flex;
  align-items: center;
  flex-shrink: 0;
  border-radius: 999px;
  transition: opacity 0.2s ease, transform 0.2s ease;
}
.nav-logo:hover { opacity: 0.85; transform: translateY(-1px); }
.nav-profile-photo {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  object-fit: cover;
  object-position: center 28%;
  border: 2px solid var(--border);
  box-shadow: 0 6px 18px rgba(15, 23, 42, 0.12);
  display: block;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 0.25rem;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.4rem 0.75rem;
  border-radius: 6px;
  transition: color 0.2s ease, background 0.2s ease;
}
.nav-links a:hover {
  color: var(--text);
  background: var(--accent-light);
}

.nav-right { display: flex; align-items: center; gap: 0.75rem; }

.theme-toggle {
  width: 36px; height: 36px;
  border: 1px solid var(--border);
  background: var(--bg);
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  color: var(--text-secondary);
  transition: all 0.2s ease;
  position: relative;
}
.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }

.sun-icon, .moon-icon {
  position: absolute;
  transition: transform 0.3s ease, opacity 0.3s ease;
}
[data-theme="light"] .moon-icon { transform: rotate(90deg); opacity: 0; }
[data-theme="light"] .sun-icon  { transform: rotate(0deg);  opacity: 1; }
[data-theme="dark"]  .sun-icon  { transform: rotate(-90deg); opacity: 0; }
[data-theme="dark"]  .moon-icon { transform: rotate(0deg);  opacity: 1; }

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 4px;
}
.hamburger span { width: 22px; height: 2px; background: var(--text); border-radius: 2px; transition: all 0.3s ease; }
.hamburger.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.hamburger.active span:nth-child(2) { opacity: 0; }
.hamburger.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ─── Hero ───────────────────────────────────────────────────── */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 6rem 2rem 4rem;
  position: relative;
  text-align: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-light);
  border: 1px solid rgba(37, 99, 235, 0.2);
  padding: 0.35rem 0.9rem;
  border-radius: 100px;
  margin-bottom: 1.75rem;
  letter-spacing: 0.01em;
}
[data-theme="dark"] .hero-badge { border-color: rgba(88, 166, 255, 0.25); }

.hero-greeting {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1.1;
  margin-bottom: 1rem;
}

.hero-typing {
  font-size: clamp(2.5rem, 8vw, 5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 1rem;
  min-height: 1.2em;
  color: var(--accent);
}

.typing-text { display: inline-block; }
.typing-cursor {
  display: inline-block;
  color: var(--accent);
  animation: blink 1s infinite;
  font-weight: 300;
}
@keyframes blink { 0%,50%{opacity:1} 51%,100%{opacity:0} }

.hero-tagline {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 2.5rem;
}

.hero-links { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }

.hero-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.7rem 1.5rem;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  transition: all 0.2s ease;
  cursor: pointer;
  border: none;
}
.hero-btn--primary {
  background: var(--accent);
  color: #fff;
}
.hero-btn--primary:hover { opacity: 0.88; transform: translateY(-1px); }
.hero-btn--ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}
.hero-btn--ghost:hover { border-color: var(--accent); color: var(--accent); transform: translateY(-1px); }

.scroll-indicator {
  position: absolute;
  bottom: 2.5rem;
  left: 50%;
  transform: translateX(-50%);
  color: var(--text-secondary);
  animation: bounce 2s infinite;
  opacity: 0.5;
}
@keyframes bounce {
  0%,100%{ transform: translateX(-50%) translateY(0); }
  50%{ transform: translateX(-50%) translateY(-8px); }
}

/* ─── Sections ───────────────────────────────────────────────── */
.section { padding: 7rem 2rem; position: relative; }

.container { max-width: 1200px; margin: 0 auto; }

.section-number {
  position: absolute;
  top: 3rem; left: 2rem;
  font-size: 8rem;
  font-weight: 800;
  color: var(--border);
  opacity: 0.4;
  pointer-events: none;
  z-index: 0;
  line-height: 1;
  letter-spacing: -0.05em;
  user-select: none;
}

.section-title {
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  font-weight: 700;
  margin-bottom: 3rem;
  letter-spacing: -0.03em;
  position: relative;
}
.section-title::after {
  content: '';
  display: block;
  width: 2.5rem;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
  margin-top: 0.75rem;
}

/* ─── About ──────────────────────────────────────────────────── */
.about-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr;
  gap: 5rem;
  align-items: start;
}

.about-bio p {
  font-size: 1.05rem;
  line-height: 1.85;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

.about-highlights {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
  margin-top: 1.5rem;
}

.highlight-item {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text);
  padding: 0.65rem 0.9rem;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: 8px;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.highlight-item svg { color: var(--accent); flex-shrink: 0; }
.highlight-item:hover { border-color: var(--accent); background: var(--accent-light); }

.about-info { display: flex; flex-direction: column; gap: 1.25rem; }

.info-item { display: flex; flex-direction: column; gap: 0.2rem; }

.info-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
  font-weight: 600;
}

.info-value {
  font-size: 0.95rem;
  color: var(--text);
  transition: color 0.2s ease;
}
a.info-value:hover { color: var(--accent); }

/* ─── Skills ─────────────────────────────────────────────────── */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2.5rem 3rem;
}

.skill-group { display: flex; flex-direction: column; gap: 0.75rem; }

.skill-group-title {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.skill-tags span {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text);
  background: var(--bg-alt);
  border: 1px solid var(--border);
  padding: 0.3rem 0.7rem;
  border-radius: 6px;
  transition: all 0.2s ease;
}
.skill-tags span:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-light); }

/* ─── Projects ───────────────────────────────────────────────── */
.project-filters {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 2.5rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.45rem 1rem;
  font-size: 0.85rem;
  font-weight: 500;
  background: var(--bg-alt);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s ease;
}
.filter-btn:hover { border-color: var(--accent); color: var(--text); }
.filter-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }

.projects-list { display: flex; flex-direction: column; }

.project-item {
  display: grid;
  grid-template-columns: 3.5rem 1fr;
  gap: 1.5rem;
  padding: 1.75rem 0;
  border-bottom: 1px solid var(--border);
  cursor: pointer;
  transition: all 0.2s ease;
}
.project-item:last-child { border-bottom: none; }
.project-item.hidden { display: none; }
.project-item:hover { background: var(--accent-light); margin: 0 -1.5rem; padding-left: 1.5rem; padding-right: 1.5rem; border-radius: 10px; border-bottom-color: transparent; }

.project-left {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.4rem;
  padding-top: 0.2rem;
}

.project-number {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-secondary);
  font-variant-numeric: tabular-nums;
}

.project-award {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--accent);
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.project-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.5rem;
}

.project-info h3 {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.3;
}

.project-link {
  font-size: 1rem;
  color: var(--text-secondary);
  flex-shrink: 0;
  transition: color 0.2s ease;
  margin-top: 0.1rem;
}
.project-link:hover { color: var(--accent); }

.project-info p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 0.85rem;
}

.project-tags { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.project-tags span {
  font-size: 0.75rem;
  color: var(--text-secondary);
  background: var(--bg-alt);
  border: 1px solid var(--border);
  padding: 0.2rem 0.55rem;
  border-radius: 4px;
}

/* ─── Modal ──────────────────────────────────────────────────── */
.modal {
  display: none;
  position: fixed;
  top: 0; left: 0;
  width: 100%; height: 100%;
  z-index: 2000;
  align-items: center;
  justify-content: center;
}
.modal.active { display: flex; }

.modal-overlay {
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background: rgba(0,0,0,0.7);
  backdrop-filter: blur(4px);
}

.modal-content {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  max-width: 640px;
  width: 92%;
  max-height: 80vh;
  overflow-y: auto;
  position: relative;
  z-index: 1;
  padding: 2.5rem;
  box-shadow: var(--shadow-md);
  animation: slideUp 0.25s ease;
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}

.modal-close {
  position: absolute;
  top: 1.25rem; right: 1.25rem;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-secondary);
  background: none;
  border: none;
  line-height: 1;
  transition: color 0.2s ease;
  width: 32px; height: 32px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 6px;
}
.modal-close:hover { color: var(--text); background: var(--bg-alt); }

.modal-body h3 { font-size: 1.4rem; margin-bottom: 0.75rem; letter-spacing: -0.02em; }
.modal-body p { font-size: 1rem; line-height: 1.75; color: var(--text-secondary); margin-bottom: 1rem; }
.modal-body ul { list-style: none; padding: 0; margin: 1rem 0; }
.modal-body li {
  padding-left: 1.25rem;
  margin-bottom: 0.6rem;
  position: relative;
  color: var(--text-secondary);
  line-height: 1.6;
  font-size: 0.95rem;
}
.modal-body li::before { content: '▸'; position: absolute; left: 0; color: var(--accent); }

/* ─── Experience Tabs ────────────────────────────────────────── */
.experience-tabs {
  display: flex;
  gap: 0;
  margin-bottom: 2.5rem;
  border-bottom: 1px solid var(--border);
}

.tab-btn {
  padding: 0.75rem 1.5rem;
  font-size: 0.9rem;
  font-weight: 500;
  background: none;
  color: var(--text-secondary);
  border: none;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  cursor: pointer;
  transition: all 0.2s ease;
}
.tab-btn:hover { color: var(--text); }
.tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }

.tab-content { display: none; }
.tab-content.active { display: block; animation: fadeIn 0.3s ease; }
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ─── Timeline ───────────────────────────────────────────────── */
.timeline { position: relative; padding-left: 7rem; }
.timeline::before {
  content: '';
  position: absolute;
  left: 3.5rem; top: 0;
  height: 100%; width: 1px;
  background: var(--border);
}

.timeline-item { position: relative; margin-bottom: 3rem; }
.timeline-item:last-child { margin-bottom: 0; }

.timeline-year {
  position: absolute;
  left: -7rem; top: 0.1rem;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent);
  width: 3.5rem;
  text-align: right;
}

.timeline-content { padding-left: 2rem; }
.timeline-content h3 { font-size: 1.1rem; font-weight: 600; margin-bottom: 0.2rem; letter-spacing: -0.01em; }
.timeline-content h4 { font-size: 0.9rem; font-weight: 500; color: var(--accent); margin-bottom: 0.35rem; }
.timeline-meta { font-size: 0.8rem; color: var(--text-secondary); margin-bottom: 0.75rem; }

.timeline-content ul { list-style: none; padding: 0; margin: 0; }
.timeline-content li {
  padding-left: 1.25rem;
  margin-bottom: 0.4rem;
  position: relative;
  color: var(--text-secondary);
  line-height: 1.6;
  font-size: 0.9rem;
}
.timeline-content li::before { content: '▸'; position: absolute; left: 0; color: var(--accent); font-size: 0.75rem; top: 0.15rem; }

/* ─── Publications ───────────────────────────────────────────── */
.publications-list { display: flex; flex-direction: column; gap: 2.5rem; }

.publication-item {
  padding: 1.75rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}
.publication-item:hover { border-color: var(--accent); box-shadow: var(--shadow-md); }

.pub-venue {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.publication-item h3 { font-size: 1.1rem; font-weight: 600; margin-bottom: 0.5rem; letter-spacing: -0.01em; }

.pub-authors {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
  line-height: 1.5;
}

.publication-item p { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.65; }

/* ─── Contact ────────────────────────────────────────────────── */
.contact-center { text-align: center; max-width: 560px; margin: 0 auto; }

.contact-email {
  font-size: clamp(1.4rem, 3.5vw, 2.25rem);
  font-weight: 700;
  color: var(--text);
  display: inline-block;
  margin-bottom: 1.5rem;
  letter-spacing: -0.03em;
  transition: color 0.2s ease;
}
.contact-email:hover { color: var(--accent); }

.contact-status { font-size: 1rem; color: var(--text-secondary); margin-bottom: 0.5rem; line-height: 1.6; }
.contact-location { font-size: 0.9rem; color: var(--text-secondary); margin-bottom: 2rem; }

.contact-social { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }
.contact-social a {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 0.55rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  transition: all 0.2s ease;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}
.contact-social a:hover { color: var(--accent); border-color: var(--accent); background: var(--accent-light); }

/* ─── Footer ─────────────────────────────────────────────────── */
.footer {
  padding: 3rem 2rem;
  text-align: center;
  border-top: 1px solid var(--border);
}
.footer p { font-size: 0.85rem; color: var(--text-secondary); }

/* ─── Scroll Animations ──────────────────────────────────────── */
.fade-in {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ─── Responsive ─────────────────────────────────────────────── */
@media (max-width: 1024px) {
  .about-grid { grid-template-columns: 1fr; gap: 3rem; }
  .skills-grid { grid-template-columns: 1fr; gap: 2rem; }
  .about-highlights { grid-template-columns: 1fr 1fr; }
  .timeline { padding-left: 5.5rem; }
  .timeline::before { left: 2.75rem; }
  .timeline-year { left: -5.5rem; width: 2.75rem; }
}

@media (max-width: 768px) {
  .nav-links {
    position: fixed;
    left: -100%;
    top: 61px;
    flex-direction: column;
    background: var(--bg);
    width: 100%;
    padding: 1.5rem 2rem;
    gap: 0.25rem;
    border-bottom: 1px solid var(--border);
    transition: left 0.3s ease;
    z-index: 999;
  }
  .nav-links.active { left: 0; }
  .nav-links a { padding: 0.6rem 0.75rem; font-size: 1rem; }
  .hamburger { display: flex; }

  .section { padding: 5rem 1.5rem; }
  .section-number { font-size: 5rem; left: 1.5rem; }

  .project-item:hover { margin: 0; padding-left: 0; padding-right: 0; border-radius: 0; border-bottom: 1px solid var(--border); background: transparent; }
  .project-item:hover:last-child { border-bottom: none; }

  .timeline { padding-left: 0; }
  .timeline::before { display: none; }
  .timeline-year { position: static; width: auto; margin-bottom: 0.35rem; text-align: left; }
  .timeline-content { padding-left: 0; }

  .modal-content { padding: 1.75rem; width: 95%; }
  .experience-tabs { flex-wrap: wrap; }
  .tab-btn { flex: 1; min-width: 120px; text-align: center; }
  .about-highlights { grid-template-columns: 1fr; }
  .project-filters { gap: 0.4rem; }
  .filter-btn { flex: 1; min-width: 80px; text-align: center; }
}

@media (max-width: 480px) {
  .nav-inner { padding: 0.875rem 1.25rem; }
  .section { padding: 4rem 1.25rem; }
  .section-number { font-size: 3.5rem; }
  .hero-greeting { font-size: 2.25rem; }
  .contact-email { font-size: 1.35rem; }
  .about-highlights { grid-template-columns: 1fr; }
}